1. Field of the Invention
This invention relates to a flow controller for an aerosol container, used suitably for an aerosol product, like an aerosol product using a compression gas such as a carbonate gas or the like as a propellant, that otherwise tends to lose spraying pressure inside the aerosol container as aerosol contents are more sprayed.
2. Description of Related Art
Aerosol products have been categorized, based on a propellant, into products using liquefied gas and products using compression gas such as carbonate gas or the like. The aerosol products using liquefied gas as a propellant have a high expansion ratio of gas vaporization, and therefore, even if the aerosol contents are sprayed continuously for a considerable amount of time, the pressure in the aerosol container remains unchanged and is rarely reduced.
To the contrary, where a compression gas such as carbonate gas is used as a propellant in an aerosol container, the aerosol container can spray aerosol contents with a strong pressure at an initial stage of the use of the container. As the aerosol container sprays further aerosol contents, however, a headspace where the gas can exist becomes larger, thereby rendering the compression gas dispersed in the widened headspace, and reducing the pressure in the aerosol container. The spraying amount per unit time of the aerosol contents decreases in proportion to a decrease of the pressure in the aerosol container, thereby becoming subject to a large gap between the initial stage and later stage upon subsequent continuous use, rendering use of the aerosol container less satisfactory.
To eliminate such a problem, an invention was devised as disclosed in Japanese Unexamined Patent Publication (KOKAI) Heisei No.8-58,859. With this invention, a flow controller for controlling the flow amount of aerosol contents is arranged at a lower end of a valve assembly of an aerosol container or at a lower end of a dip tube connected to a valve assembly as a separate body from the valve assembly or the dip tube.
This conventional flow controller has a piston's controlling sleeve slidably inserted in a cylinder, and the flow amount of the aerosol contents is controlled by communication resistance occurring at a passage space formed between an inner round surface of the cylinder and an outer round surface of the controlling sleeve while the controlling sleeve is inserted. Where the aerosol container keeps a high pressure at an initial stage of spraying the aerosol contents, the piston is pushed toward an outlet side chamber by this pressure and slides to deeply insert the controlling sleeve. Since the communication resistance of the passage space becomes larger as the inner round surface of the piston faces to the outer round surface of the controlling sleeve with a larger area, the high pressure of the aerosol container results in a high communication resistance, thereby suppressing the flow amount of the aerosol contents.
To the contrary, where the aerosol contents are further sprayed and the headspace is made larger, the pressure in the aerosol container is made lower, thereby reducing the pressure onto the piston. The reduced pressure on the piston reduces an insertion amount of the controlling sleeve in the cylinder. According to this reduction of the insertion amount, the communication resistance of the passage space is reduced, thereby allowing the aerosol contents to pass more through the passage space. Thus, the flow controller controls the flow amount of the aerosol contents in proportion to the pressure in the aerosol container, thereby maintaining the spray amount of the aerosol contents per unit time at a constant amount.
With such a conventional flow controller, however, the flow controller is assembled as a separate body from the valve assembly, so that manufacturing of the flow controller is laborious and requires materials, resulting in high costs. Such a controller may also need a process to attach the controller to the dip tube. Where the controller is attached to the dip tube, weight of the flow controller may unexpectedly bend and break the dip tube when the aerosol container is tilted during use of the container.
As another conventional controller, an invention disclosed in Japanese Unexamined Patent Publication (KOKAI) Heisei No. 7-242,280, has a flow controller within a housing of a valve assembly. With this controller, a piston disposed on an inlet side chamber of the housing slides according to pressure in an aerosol container and compresses an elastic body disposed on an outlet side to restrict the flow amount of the aerosol contents passing through a bubble portion of the elastic body, thereby controlling the flow amount.
The controller incorporated in the housing may reduce labors and costs for the manufacturing process, in comparison with the art in Japanese Unexamined Patent Publication Showa No. 8-58,859. This controller, however, brings disfavored results in which the aerosol contents are in contact with the elastic body, thereby causing the elastic body to be impaired and to lose the elasticity, or thereby clogging the passages, and further this controller may encounter with loss of controllability of the flow amount.